1. Field of the Invention
The present invention relates to an occupant detecting system including at least one sheet-shaped sensor fixed to a seat back to detect the sitting attitude and the physical constitution of an occupant.
2. Description of the Related Art
When a child sitting on a front passenger""s seat has fallen asleep and has been inclined toward a door, the following problem is encountered: The head of the child having a low sitting height is disposed very near the front of a side air bag device accommodated in a side of a seat back and for this reason, a side air bag cannot be deployed effectively. Therefore, there is an occupant detecting system already proposed by the present assignee(see Japanese Patent Application Laid-open No. 10-3938), in which a sheet-shaped sensor is embedded between a pad of a seat back and a trim cover covering the surface of the pad to detect the sitting attitude and the physical constitution of an occupant sitting on a front passenger""s seat, and when a child is in a sleeping attitude leaning toward a door, the operation of a side air bag device is prohibited.
To mount a sensor to a pad of a seat back, a method sing an adhesive, a method using a double-coated adhesive tape or a method using a double-adhesive applying treatment is conventionally employed.
However, the method for mounting the sensor using the adhesive suffers from a disadvantage that many steps of adhesive applicationxe2x86x92affixingxe2x86x92pressingxe2x86x92drying are required and as a result, the time required for the mounting operation is prolonged. Also, the quality becomes unstable due to variability in amount and position of adhesive applied. Moreover, when an organic solvent-containing adhesive is used, an undesirable influence to the working environment is feared from the evaporated solvent. When a double-coated adhesive tape or a double-adhesive applying treatment is employed, problems are encountered such as a reduction in adhesive force caused when the sensor is exposed to a high temperature, and reduction durability due to chemicals in the adhesive.
A sensor including a conductive fabric (a fabric plated with a metal) adhered to a base fabric is conventionally used.
However, the conventional sensor suffers the following disadvantages: A special catalyst is required when the fabric is subjected to the metal plating. Moreover, a laser fusing is required for cutting in order to prevent a short-circuit due to fraying of an end edge of the fabric, and further, a surface coating is required for enhancing the corrosion resistance of a metal-plated portion. For this reason, the manufacturing cost is extremely increased.
Accordingly, it is a first object of the present invention to ensure that a sensor for an occupant detecting system can be fixed easily and reliably to a seat back.
It is a second object of the present invention to provide a sensor for an occupant detecting system at a low cost.
To achieve the above first object, according to a first aspect and feature of the present invention, there is provided an occupant detecting system comprising at least one sheet-shaped sensor fixed to a seat back to detect the sitting attitude and the physical constitution of an occupant, wherein the sensor is welded to the seat back with a hot-melt film interposed therebetween.
With the above arrangement, when the hot-melt film is molten, the sensor can be easily fixed to the seat back by only superposing and heat-pressing the hot-melt film and the sensor to the seat back. Thus, the time required for the fixing operation can be shortened remarkably relative to the conventional mounting method to reduce the cost, and the sensor can be fixed reliably and firmly to the seat back, while eliminating any adverse influence to the working or operating environment.
To achieve the above first object, according to a second aspect and feature of the present invention, in addition to the first feature, the hot-melt film is temporarily welded or bonded in advance to the sensor.
With the above arrangement, the hot-melt film is integrally bonded in advance to the sensor by the temporary welding. Therefore, the operation of superposing the hot-melt film and the sensor to the seat back can be facilitated to prevent the occurrence of a misalignment and to thereby enhance the operability of mounting the sensor.
To achieve the above second object, according to a third aspect and feature of the present invention, there is provided an occupant detecting system comprising at least one sheet-shaped sensor fixed to a seat back to detect the sitting attitude and the physical constitution of an occupant, wherein the sensor comprises a conductive layer printed on a surface of a film material.
With the above arrangement, the sensor comprises the conductive layer printed on the surface of the film material and hence, the manufacturing cost can be reduced remarkably. Also the durability can be enhanced, as compared with the conventional sensor including the conductive fabric adhered to the base fabric. Moreover, the thickness of the sensor can be decreased to alleviate any sense of incompatibility felt by an occupant sitting on the seat back.
To achieve the above second object, according to a fourth aspect and feature of the present invention, in addition to the third feature, the surface of the film material or the conductive layer is covered with a protective layer.
With the above arrangement, by covering the surface of the film material or the conductive layer with the protective layer, the film material or the conductive layer can be protected from an external force and the corrosion resistance thereof can be enhanced.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.